The present disclosure relates to a gas turbine engines, and more particularly to a decoupled gas turbine engine.
Known gas turbine engines for both land based (e.g. industrial gas turbines) and aircraft applications (e.g. planes and vertical lift applications such as helicopters) typically include at least two concentrically located spools, having a common engine axis. The spools generally interconnect a compressor and a turbine section interposed by a concentrically located combustor. In a turbofan application, the engine may further include a fan that drives air along a bypass flowpath while the compressor section drives air along a core flowpath for compression and communication into the combustor then expansion through the turbine section. In a two spool application, the engine generally includes a low spool and a high spool mounted for rotation about the engine axis via several bearing structures and relative to a static engine case. The low spool generally includes an inner shaft that interconnects the fan, a low pressure compressor (“LPC”) of the compressor section and a low pressure turbine (“LPT”) of the turbine section. The inner shaft may typically be configured to drive the fan.
The high spool includes an outer shaft that interconnects a high pressure compressor (“HPC”) of the compressor section and a high pressure turbine (“HPT”) of the turbine section. The combustor is arranged between the HPC and the HPT. The concentric inner and outer shafts both rotate about the engine axis. Core airflow is compressed by the LPC then the HPC, mixed with the fuel and burned in the combustor, then expanded over the HPT and the LPT. The LPT and HPT rotationally drive the respective low spool and high spool in response to the expansion.
Unfortunately, the concentric nature of such engines makes it difficult to obtain high operating pressure ratios while maintaining/achieving small engine core size. Further, packaging space for the engine may be limited, and achieving optimal dimensional tolerances with known manufacturing techniques may be difficult to obtain especially for smaller engines.